Four ALMA antennas on the Chajnantor plateau

Time-lapse of a whole night at the ALMA Array Operations Site (AOS), located at 5000 metres altitude on the Chajnantor plateau, in the II Region of Chile, where three of the first ALMA antennas are being tested as part of the ongoing Commissioning and Science Verification process. Because they are pointing at the same target in the sky at any moment, their movements are perfectly synchronised. A bright crescent Moon lights the landscape during the first half of the night. As the Moon sets, the Milky Way becomes more visible on the left of the image. The “Coal Sack” dark nebula, together with the emblematic constellation of the Southern Cross, is followed by the bright stars Alpha and Beta Centauri. The fact that several stars in the image seem to increase and decrease their brightness is due to the passing of thin high clouds. As the sky appears to rotate clockwise around the south celestial pole (beyond the left edge of the image), the Milky Way appears on the upper edge and goes down slowly, until it is lying almost horizontal before sunrise. The centre of our galaxy becomes visible during the second half of the night as a yellowish bulge crossed by dark lanes in the centre of the image, just above the antennas. ALMA, the Atacama Large Millimeter/submillimeter Array, is the largest astronomical project in existence and is a global partnership between the scientific communities of East Asia, Europe and North America with Chile. ESO is the European partner in ALMA.

This sequence is available in 1080p and stereoscopic 3D from José Francisco Salgado (josefrancisco.org).